Table 4.

Predictive statistics derived using the regression tree method and associated parameters when creating predictive models of percentages of total nitrogen and carbon, carbonate, and organic matter using spectral bands between 400 and 1,000 nm for different soil series and horizons from Washington and Oregon.

Soil Property	R2	p statistic	Relative Error	Cross Validation Error	Complexity Parameter	Spectral Bands (nm)
						First Split	Second Split	Third Split	Fourth Split
Total Nitrogen	0.91	p < 0.01	0.09	0.35	0.01	470	846	403, 687	515
Carbonate	0.96	p < 0.01	0.71	0.71	0.17	531	898
Total Carbon	0.93	p < 0.01	0.07	1.37	0.04	441	907, 400	409
Organic Matter	0.98	p < 0.01	0.02	1.16	0.01	441	907, 400	832, 300